The present invention relates to a new, stable, substantially anhydrous crystalline sodium (5R,6S,8R)-6-(1-hydroxyethyl)-2-(2-carbamoyloxyethylthio)-penem-3-carboxyl ate and processes for its preparation. The crystalline compound exhibits highly desirable physical stability and solid state chemical stability and reduced hygroscopicity which are unexpected and superior to that of amorphous sodium (5R,6S,8R)-6-(1-hydroxyethyl)-2-(2-carbamoyloxyethylthio)-penem-3-carboxyl ate.
The amorphous compound is useful as a broad spectrum antibacterial effective against beta-lactamase-producing strains. It is prepared by procedures disclosed in U.S. Pat. No. 4,504,485 which patent is hereby incorporated by reference.
The amorphous sodium salt of the subject penem carboxylate has an unsatisfactory shelf-life as compared to extended shelf-life times mandated by the U.S. Food and Drug Administration because it is deliquescent and heat sensitive. These properties make it difficult to prepare and store as clinically suitable formulations.